Bolt-in adjustable crossmember for 1963-1987 Chevy and GMC C10 and C20 2WD trucks, sized for TH350, TH400, 700R4, 4L60E and 4L80E swaps.
Swapping a TH350 or Powerglide out of a 1963-1987 Chevy or GMC C10, C20, Blazer or Suburban for a 700R4, 4L60E, 4L80E or 6L80 is one of the most common upgrades on these trucks, and the first thing that stops the job is the crossmember. The factory piece puts the mount where the short original case ended. A longer overdrive case puts its tail pad somewhere else, and you end up drilling the frame or shimming a mount at an angle. This adjustable tubular crossmember bolts into the 2WD frame and slides fore and aft so the mount lands under whichever case you are installing.
Novak lists the TH350 case at 21-3/4 in long, the 700R4 at 23-3/8 in and the TH400 at 24-3/8 in. That means a 700R4 or early 4L60E puts its rear mount about 1-5/8 in further back than the TH350 it replaces, and a TH400 about 2-5/8 in further back, before you even get to the longer electronic units. The crossmember carries the back of the engine and transmission, so where the mount sits also sets the driveline angle. A mount that is forced into place or left hanging puts the output shaft at the wrong angle, and that shows up as vibration and early wear on the U-joints and tailhousing bushing.
Know the exact transmission you are installing and measure your frame rail spacing. The crossmember solves the mount, but each overdrive swap brings its own wiring and control. A 700R4 needs a correctly set TV cable, and a 4L60E needs a computer to shift it, plus a range switch and a working internal harness. Our 4L60E common problems guide covers what to check on a used core before it goes in, and the 4L60E shift problems guide helps if it shifts wrong after the swap.
This crossmember fits 1963-1987 Chevrolet and GMC C10 and C20 two-wheel-drive trucks, including the 2WD Blazer and Suburban, and it replaces Classic Performance style CP-1108G. The pad accepts the TH350, TH400, 700R4, 4L60, 4L60E, 4L65E, 4L70E, 4L75E, 4L80E, 6L80 and 6L90 with the included GM-type rubber mount and hardware. It is built from 2 in bent steel tube with 1/4 in plates and a black anti-rust finish. It does not fit 4x4 K-series trucks, which use a different rear mount location. Novak notes the later 4L60E changed its tailhousing pattern from the four-bolt 700R4 style, so confirm the mount bolts to your case. Questions about your truck? Send the year and VIN. More swap and rebuild parts are on our 4L60E page.
If the swap is a 4L60E, plan for the electrical side at the same time: a 4L60E/4L80E range switch and a Rostra internal harness with TCC solenoid are cheap insurance on a used core.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is made for 1963-1987 C10 and C20 two-wheel-drive trucks, including the 2WD Blazer and Suburban. The 4x4 trucks place the rear mount differently and this crossmember will not adapt to them.
Usually yes. The 700R4 case is about 1-5/8 in longer than the TH350, and the yoke position changes with it. Install the transmission and set the crossmember first, then measure from the yoke to the rear axle flange for the new shaft length.
Yes. It ships with a standard GM-type rubber rear transmission mount and the mounting hardware, so the only thing you need to supply is the transmission.
The tubing is bent to clear long-tube headers and exhaust up to 4 in. On a lowered truck it sits above the frame rails, so it does not hang below the frame and drag.
Yes. It bolts into the existing frame holes on most trucks, but it can be welded in if the frame has been boxed or the original holes are worn oversize. Set the mount position and driveline angle before you weld.
